U.S. patent number 8,208,645 [Application Number 11/521,635] was granted by the patent office on 2012-06-26 for system and method for harmonizing calibration of audio between networked conference rooms.
This patent grant is currently assigned to Hewlett-Packard Development Company, L.P.. Invention is credited to Scott Grasley, David R Ingalls, William Mcconnell, Masoud Zavarehi.
United States Patent |
8,208,645 |
Ingalls , et al. |
June 26, 2012 |
System and method for harmonizing calibration of audio between
networked conference rooms
Abstract
A system and method is disclosed for harmonizing calibration of
audio between a plurality of networked conference rooms to enable
each networked conference room to have substantially similar audio
characteristics by adjusting speaker gain output of an audio signal
sent from a calibration location on a network and tuning microphone
response received at a calibration location to a calibrated audio
source.
Inventors: |
Ingalls; David R (Corvallis,
OR), Grasley; Scott (Lebanon, OR), Mcconnell; William
(Benton County, OR), Zavarehi; Masoud (Corvallis, OR) |
Assignee: |
Hewlett-Packard Development
Company, L.P. (Houston, TX)
|
Family
ID: |
39181810 |
Appl.
No.: |
11/521,635 |
Filed: |
September 15, 2006 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080071861 A1 |
Mar 20, 2008 |
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Current U.S.
Class: |
381/58; 381/59;
381/71.12 |
Current CPC
Class: |
H04M
3/568 (20130101); H04M 3/56 (20130101); H04M
7/12 (20130101) |
Current International
Class: |
H04R
29/00 (20060101) |
Field of
Search: |
;381/56,58,59,60,77,95,96,71.12 ;379/202.01 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0018099 |
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Mar 2000 |
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WO |
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WO 01/26272 |
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Apr 2001 |
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WO |
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Primary Examiner: Matar; Ahmad
Assistant Examiner: Asanbayev; Oleg
Claims
What is claimed is:
1. A method for harmonizing calibration of audio between a
plurality of networked conference rooms, comprising: a) calibrating
a speaker output level of conference speakers within each networked
conference room of the plurality of networked conference rooms by:
(1) transmitting an audio reference signal to each conference
speaker over a network from a calibration studio on the network;
and (2) adjusting a speaker gain of each conference speaker to
enable the audio reference signal emitted by each conference
speaker to be within a predetermined output level; b) separately
calibrating a microphone input level of conference microphones
within each networked conference room of the plurality of networked
conference rooms by: (1) emitting a tone signal from a single
calibrated reference speaker, different from the conference
speakers, within each networked conference room of the plurality of
networked conference rooms into each conference microphone to
generate a tone level signal from each conference microphone; (2)
transmitting each tone level signal from the plurality of networked
conference rooms to the calibration studio; and (3) adjusting a
microphone gain of each conference microphone such that the tone
level signal at the calibration studio is within a predetermined
input level.
2. A method as in claim 1, further comprising successively
transmitting a standardized audio signal from the calibration
studio over the network to the conference speaker within each
networked conference room of the plurality of networked conference
rooms to enable each successive conference speaker to emit the
standardized audio signal.
3. A method as in claim 2, further comprising detecting the emitted
standardized audio reference signal from each successive conference
speaker with each successive conference microphone within each
networked conference room of the plurality of networked conference
rooms to form an array of signature signals, wherein the array of
signature signals comprises a measurement of the standardized audio
signal of each successive conference speaker by each successive
conference microphone within each networked conference room of the
plurality of networked conference rooms.
4. A method as in claim 3, further comprising storing the array of
signature signals for each networked conference room of the
plurality of networked conference rooms in a database located on
the network to form a networked conference room calibration
standard for each networked conference room of the plurality of
networked conference rooms.
5. A method as in claim 4, further comprising periodically
verifying a selected networked conference room calibration standard
by comparing a newly measured array of signature signals for a
selected networked conference room of the plurality of networked
conference rooms with the networked conference room calibration
standard for the selected networked conference room.
6. A method as in claim 5, further comprising adjusting a
conference speaker gain or conference microphone gain when a
calibration difference between signature signals in the newly
measured array and the networked conference room calibration
standard is greater than a predetermined calibration difference
amount.
7. A method as in claim 6, further comprising adjusting the
conference speaker gain by the calibration difference when the
calibration difference for the conference speaker, as measured by
the conference microphone within the same networked conference
room, is the same across the conference speakers within the same
networked conference room.
8. A method as in claim 6, further comprising adjusting the
conference microphone gain by the calibration difference when the
calibration difference for the conference microphone, as measured
by the conference speaker within the same networked conference
room, is the same across the conference microphones within the same
networked conference room.
9. A method as in claim 1, wherein transmitting the audio reference
signal further comprises transmitting the audio reference signal to
the conference speaker, wherein the audio reference signal is
configured to enable the conference speaker to emit pink noise.
10. A system for harmonizing calibration of audio between a
plurality of networked conference rooms, comprising: a calibration
studio coupled to a network; a conference speaker within each
networked conference room of the plurality of networked conference
rooms, said conference speaker configured to emit an audio
reference signal transmitted from the calibration studio over the
network to the conference speaker; a sound pressure meter within
each networked conference room of the plurality of networked
conference rooms, said sound pressure meter configured to measure
the audio reference signal emitted by the conference speaker to
enable speaker gain of the conference speaker to be adjusted until
the emitted audio reference signal is within a predetermined output
level; a conference microphone located within each networked
conference room of the plurality of networked conference rooms; a
single calibrated reference speaker, different from the conference
speaker, within each networked conference room of the plurality of
networked conference rooms, configured to emit a calibrated
reference tone into the conference microphone to generate a tone
level signal from the conference microphone; and wherein the
calibration studio is further configured to receive and measure a
level of the tone level signal emitted from the conference
microphone within each networked conference room of the plurality
of networked conference rooms to enable a microphone gain of the
conference microphone to be calibrated to within a predetermined
input level.
11. A system as in claim 10, wherein the calibration studio further
comprises a codec configured to encode the audio reference signal
prior to transmitting and decode the received tone level
signal.
12. A system as in claim 10, wherein the calibration studio is
further configured to emit an audio reference signal comprised of
pink noise.
13. A system as in claim 10, further comprising a plurality of M
conference microphones and a plurality of N conference speakers
within each networked conference room of the plurality of networked
conference rooms.
14. A system as in claim 13, further comprising a networked
conference room calibration standard for each networked conference
room of the plurality of networked conference rooms, comprising an
M times N array of measurements comprising successive measurements
of a standardized audio output of each of the plurality of N
conference speakers by each of the plurality of M conference
microphones within each networked conference room.
15. A system as in claim 14, further comprising a calibration
check, wherein a calibration check measurement comprises an M times
N array of measurements comprising successive measurements of the
standardized audio output of each of the plurality of N conference
speakers by each of the plurality of M conference microphones
within each networked conference room.
16. A system as in claim 15, wherein the microphone gain of a
calibration checked microphone is adjusted when a calibration
checked microphone gain changes more than a predetermined amount
from the networked conference room calibration standard.
17. A system as in claim 15, wherein the calibration studio is
configured to adjust the microphone gain of the calibration checked
microphone when the calibration checked microphone gain in the
calibration check has substantially the same change in measurement
of each conference speaker within the plurality of N conference
speakers when compared with the networked conference room
calibration standard.
18. A system as in claim 15, wherein the speaker gain of a
calibration checked speaker is adjusted when the calibration
checked speaker gain changes more than a predetermined amount from
the networked conference room calibration standard.
19. A system as in claim 15, wherein the calibration station is
configured to adjust the speaker gain of the calibration checked
speaker when the calibration checked speaker gain in the
calibration check has substantially the same change in measurement
by each conference microphone within the plurality of M conference
microphones when compared with the networked conference room
calibration standard.
20. A method of making a harmonized calibration system having a
standardized audio calibration, comprising: a) providing a
plurality of networked conference rooms; b) calibrating a speaker
output level of conference speakers within each networked
conference room of the plurality of networked conference rooms by:
(1) transmitting an audio reference signal to the conference
speakers over a network from a calibration studio on the network;
and (2) adjusting a speaker gain of the conference speakers to
enable the audio reference signal emitted by the conference speaker
to be within a predetermined output level; c) separately
calibrating a microphone input level of conference microphones
within each networked conference room of the plurality of networked
conference rooms by: (1) placing a single calibrated reference
speaker, different from the conference speaker, proximate to the
conference microphones; (2) emitting a tone signal from the
calibrated reference speaker within each networked conference room
of the plurality of networked conference rooms into each conference
microphone to cause each conference microphone to generate a tone
level signal; (3) transmitting each tone level signal from the
plurality of networked conference rooms to the calibration studio;
and (4) adjusting a microphone gain of each conference microphone
such that the tone level signal at the calibration studio is within
a predetermined input level.
21. A non-transitory computer usable storage medium having computer
readable program code embodied therein for harmonizing calibration
of audio between a plurality of networked conference rooms, the
computer readable program code in a computer program product
comprising: a) calibrating a speaker output level of conference
speakers within each networked conference room of the plurality of
networked conference rooms using: (1) instructions for transmitting
an audio reference signal to each conference speaker over a network
from a calibration studio on the network; and (2) instructions for
adjusting speaker gain of each conference speaker to enable the
audio reference signal emitted by each conference speaker to be
within a predetermined output level; b) separately calibrating a
microphone input level of conference microphones within each
networked conference room of the plurality of networked conference
rooms using: (1) instructions for emitting a tone signal from a
single calibrated reference speaker, different from the conference
speakers, into each conference microphone to generate a tone level
signal from each conference microphone; (2) instructions for
transmitting the tone level signal to the calibration studio; and
(3) instructions for adjusting a microphone gain of each conference
microphone such that the tone level signal at the calibration
studio is within a predetermined input level.
Description
BACKGROUND
Since the invention of the telephone people have sought to
supplement face to face meetings with conferences from remote
locations. With the advent of the internet and the greater
availability of broadband communications, it was often assumed that
remote conferencing would be the wave of the future. For example,
businesses, groups, family, and friends could communicate with each
other as if they were in the same room. Ideas and visions could be
shared without the need for cross-continent trips by business
people or other types of groups.
The realization of this dream, however, has never fully come to
fruition. Important business is often still done face to face.
Important decisions are often made only after personal
communication. And board meetings are usually held around a
conference table rather than a group of video or audio conference
rooms.
Many reasons exist for the unfulfilled realization of remote
conferencing. For example, even with the advancement of broadband
data connections and audiovisual presentation equipment, subtle
(and not so subtle) variations in acoustical properties within
various remote conference locations can lead to differences in how
conference participants are perceived. Voices can sound unnatural
and communication can seem awkward. Even small acoustical
differences between remote conference rooms can be detected by the
conference participants which can make communication seem
unnatural, causing feelings of isolation and detachment between
various participants.
The acoustical and audio variations between the remote conference
locations can reduce synergy at meetings, limit the sharing of
concepts and ideas, and disrupt the ambiance that people are
accustomed to when meeting face to face. Thus, despite the
convenience of remote conferencing, the potentially unnatural
communication between the remote locations tends to reduce the use
of remote conferencing. This is evidenced by the large percentage
of people that still spend valuable time and money traveling to
meet and communicate personally.
BRIEF DESCRIPTION OF THE DRAWINGS
Features and advantages of the invention will be apparent from the
detailed description which follows, taken in conjunction with the
accompanying drawings, which together illustrate, by way of
example, features of the invention; and, wherein:
FIG. 1a is a flow chart depicting a method for calibrating a
speaker output level of a conference speaker within the networked
conference rooms in accordance with an embodiment of the present
invention;
FIG. 1b is a flow chart depicting a method for calibrating a
microphone input level of a conference microphone at the networked
conference rooms in accordance with an embodiment of the present
invention; and
FIG. 2 is a block diagram illustrating a calibration studio
configured to harmonize calibration of audio between a plurality of
networked conference rooms in accordance with an embodiment of the
present invention.
Reference will now be made to the exemplary embodiments
illustrated, and specific language will be used herein to describe
the same. It will nevertheless be understood that no limitation of
the scope of the invention is thereby intended.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
Subtle physical and acoustical variations in conference rooms can
cause communication between remote conference rooms to sound
unnatural, potentially reducing the atmosphere gained in a personal
meeting. It is possible to attempt to adjust audio settings between
two conference rooms to enable the communication to sound more
natural. However, the addition of a third conference room, or
changes in the original conference rooms, can easily disrupt
adjustments in audio settings, causing attempts at adjustment to be
limited at best, and often futile over an extended period.
In accordance with one aspect of the invention, it has been
recognized that remote conferencing audio equipment can be
calibrated to a centralized standard. Calibrating each conference
room to this centralized standard allows the addition of extra
conference rooms that have also been calibrated to the centralized
standard. With each conference room having substantially similar
audio calibrations there can be consistency across a large network
of conferencing locations. The consistency can substantially reduce
audio variations and inconsistencies between conferencing
locations. People can communicate in real time over large distances
without feeling unnatural or awkward. The consistent audio
calibrations can enable people to remotely communicate while
feeling as if they are conversing within the same room. This allows
remote conferencing to be used for a wider variety of meetings and
communication.
FIGS. 1a and 1b provide a flow chart illustrating a method for
harmonizing calibration of audio between a plurality of networked
conference rooms to enable each networked conference room to have
substantially similar audio characteristics, in accordance with an
embodiment of the present invention. The method, shown generally at
100 comprises a two step process of calibrating a conference
speaker, as shown in block 110 in FIG. 1a, and calibrating a
conference microphone, as shown in block 140 in FIG. 1b. The terms
conference speaker and conference microphone are intended to refer
to speakers and microphones specifically used for conferencing
between the networked conference rooms. The networked conference
rooms may, of course, include additional speakers and microphones
that are not used for conferencing. Likewise, the conference
speaker(s) and microphone(s) may be used for both conferencing and
non-conferencing activities.
In one embodiment, harmonizing the calibration of audio between the
plurality of networked conference rooms can be accomplished by
calibrating an audio pipeline 200 between a calibration studio 202
and the conference rooms 206. The audio pipeline can comprise the
audio path between the calibration studio and the conference rooms.
Calibrating the entire audio path between a remote location, such
as the path between the calibration studio and the conference
rooms, can enable consistent audio calibrations for each of the
conference rooms.
The conference rooms 206 can be coupled to the calibration studio
202 by a network 204. The calibration studio can be located at a
location on the network that enables the calibration studio to
communicate with each of the conference rooms. The network can be
any type of data connection capable of carrying digital or analog
calibration signals. For example, the network can be a plain old
telephone service (POTS) connection, a broadband cable connection,
an optical fiber connection, a digital subscriber line connection,
an Ethernet connection in a local area network or wide area
network, or other types of networks configured to carry analog
signals or data at a sufficient data rate to calibrate the
plurality of networked conference rooms.
The method of calibrating a speaker output level of a conference
speaker within the networked conference rooms includes the
operation of transmitting an audio reference signal to the
conference speaker over a network from a calibration location on
the network, as shown in block 120 of FIG. 1a. For example, the
calibration studio 202, shown in FIG. 2, can include a measurement
and source generation device 212. The measurement and source
generation device can transmit an audio reference signal from the
calibration studio to a conference speaker 236 in the conference
rooms 206. The conference speaker can then emit the audio reference
signal.
The audio reference signal can be configured to enable a
standardized measurement of the audio reference signal emitted by
the conference speaker. For example, in one embodiment the audio
reference signal can be comprised substantially of pink noise. Pink
noise has an even distribution of power over a logarithmic scale
when measured in octaves. This substantially even distribution
enables the human ear to perceive that each octave has a
substantially similar volume.
The desired amplitude of the audio reference signal sent from the
calibration studio 202, and the desired output level of the
conference speaker 236 can be determined, for example, using a so
called "golden room". The golden room can be a conference room
having a desired configuration and setup. The audio reference
signal can be sent from the calibration studio to a conference
speaker within the golden room, and the speaker can be adjusted to
obtain a desired output level. The output level can be measured and
the gain of the conference speaker can be adjusted to a certain
level to have a desired output volume. Similarly, a desired gain of
the conference microphone can be set within the golden room. The
desired speaker output and microphone gain levels that are
determined in the golden room can be used to adjust the conference
speaker output and conference microphone input (gain) levels using
the calibration studio 200, which is in communication with each of
the plurality of networked conference rooms, to enable each of the
rooms to have substantially consistent audio qualities.
The audio reference signal emitted by the conference speaker 236 in
each of the networked conference rooms 206 can be measured using a
calibrated audio measurement device such as an audio spectrum
analyzer or sound pressure meter. The calibrated audio measurement
device can be positioned at a predetermined location within the
conference room 206. For example, the calibrated audio measurement
device may be located proximate to a center microphone within the
conference room. Alternatively, the calibrated audio measurement
device may be located on a tripod and placed near the location of a
conference participant's ear. Locating the audio measurement device
at a similar location within each of the conference rooms enables a
substantially similar calibration for the conference speaker in
each conference room. The use of pink noise enables the conference
speaker to be calibrated to emit the audio reference signal at a
predetermined level with a relatively consistent output over at
least a portion of the audible frequency range (typically 20 Hz to
20,000 Hz).
The method 100 further includes the operation of adjusting speaker
gain of the conference speaker to enable the audio reference signal
emitted by the conference speaker to be within a predetermined
output level, as shown in block 230 in FIG. 1a. The same method can
be used to successively calibrate a plurality of conference
speakers within each conference room. The calibration of each
conference speaker is typically accomplished independent of other
conference speakers. Each conference speaker may be calibrated with
the calibrated audio measurement device at the same predetermined
location. Alternatively, different predetermined locations may be
used for different conference speakers. For example, a first
speaker may be calibrated relative to the calibrated audio
measurement device located next to a first microphone. A second
speaker may be calibrated with the calibrated audio measurement
device next to a second microphone, and so forth. Calibrating
speakers relative to adjacent microphones enables each conference
participant positioned next to a microphone to hear audio of
similar levels from a conference speaker near that microphone.
The plurality of conference speakers can each be the same type of
speaker. Alternatively, different types of speakers can be used
within the conference room. For example, speakers having different
dynamic frequency ranges, such as a tweeter, midrange speaker, or
woofer can be used within the conference room to enable sound to be
reproduced over a broad spectrum of the audible bandwidth. In one
embodiment, each conference room can include three midrange
speakers and a woofer. The woofer can be calibrated to enable the
lower frequency sound produced by the woofer to have substantially
similar gain as higher frequency sound produced by the midrange
speakers. Alternatively, the woofer output can be adjusted to have
either a lesser or greater gain than midrange and high frequency
output, depending upon a desired use of the conference room.
The audio reference signal can be produced by the measurement and
source generation device 212 within the calibration studio 202. A
digital audio mixer 214 may be used to alter the audio reference
signal to have desired audio properties. For example, the output of
the measurement and source generation device may be sent through
the digital audio mixer and adjusted to have an output
substantially comprising pink noise. The audio reference signal can
be output from the measurement and source generation device and/or
the digital audio mixer having a predetermined output level. The
same output level can be used to calibrate each of the speakers in
each of the networked conference rooms.
The audio reference signal can be encoded using a codec 216. The
codec can be an off the shelf encoder/decoder configured to encode
and decode digital audio. The codec may be used to compress the
audio reference signal using either a lossy or lossless type
compression. For example, the audio reference signal can have a
Moving Picture Expert Group (MPEG) type encoding and compression
applied, such as MPEG 1, audio layer 2 type encoding.
Alternatively, another type of encoding and/or compression can be
used that enables the audio reference signal to be transmitted
between the calibration studio 202 and each conference room
206.
The audio reference signal transmitted from the calibration studio
202 to the conference room 206 can be received by a codec 220
configured to decode and/or decompress the audio reference signal.
The audio reference signal can be sent through an audio signal
processor 224 and through one or more amplifiers 228 to at least
one conference speaker 236. The output level of each conference
speaker can be calibrated by adjusting the amplifier output or
altering the audio reference signal using the audio signal
processor. The use of the audio signal processor enables the output
of each of the conference speakers to be tuned and calibrated over
the audible spectrum to have a desired response.
A microphone input level of a conference microphone 232 at each
networked conference room 206 can also be calibrated. The
conference microphone calibration is separate from the calibration
of the conference speaker(s) 236. The conference microphone
calibration can be accomplished either before or after the
conference speaker calibration is performed. The method 100
provides the additional operation of emitting a tone signal from a
calibrated reference speaker into the conference microphone to
generate a tone level signal from the conference microphone, as
shown in block 150 in FIG. 1b.
The calibrated reference speaker 240 is a different device than the
conference speaker 236, as shown in FIG. 2. The calibrated
reference speaker is configured to simulate speech or other types
of audio with a calibrated output level. The calibrated reference
speaker can also be referred to as a simulated mouth. The
calibrated reference speaker can be placed in a similar location as
the meeting participant and used to generate one or more types of
tones used to calibrate the conference microphone 232. This
location is typically proximate to the conference microphone. The
conference microphone can convert the output of the calibrated
reference speaker to an electronic signal, referred to as a tone
level signal.
The method 100 includes the additional operation of transmitting
the tone level signal to the calibration location, as shown in
block 160 in FIG. 1b. The tone level signal can be transmitted from
the conference microphone 232, in FIG. 2, through the audio signal
processor 224, to the codec 220 for encoding and/or compression.
The encoded/compressed tone level signal can then be transmitted
over the network 204 to the calibration studio 202. The audio
signal processor in the conference room can be used to alter the
tone level signal. For example, the audio signal processor can be
used for echo cancellation. However, signal processing such as echo
cancellation is typically not applied during calibration.
The calibration location, referred to in block 160 of FIG. 1b, is
typically the calibration studio 202. The calibration studio can be
connected to the conference room through the network 204. This
allows the calibration studio to be located anywhere that network
access to the conference room is available.
A further operation of the method 100 includes the operation of
adjusting a microphone gain of the conference microphone such that
the tone level signal at the calibration location is within a
predetermined input level, as shown in block 170 of FIG. 1b. The
tone level signal from the conference microphone is received at the
calibration station 202 in FIG. 2. The tone level signal can be
decoded by the codec 216, altered or amplified by the digital audio
mixer 214, and measured and analyzed by the measurement and source
generation device 212. The microphone gain can be adjusted until
the tone level signal measured at the calibration studio is within
predetermined parameters. As previously discussed, the
predetermined parameters can be established using a golden room to
determine desired levels for the tone level signal.
Each conference room 206 can include a plurality of conference
microphones 232. Each conference microphone can be independently
calibrated using the calibrated reference speaker 240 and
calibration studio 202 connected to each conference room through
the network 204.
The use of the calibration studio 202, located independent from
each conference room 206, enables consistent standards to be used
to calibrate the conference speaker(s) 236 and conference
microphone(s) 232 in each conference room. The same audio reference
signal can be transmitted from the calibration studio to each of
the conference rooms to enable the gain of the conference
speaker(s) in each conference room to be adjusted such that the
conference speaker(s) output at a substantially similar level.
Similarly, the calibrated reference speaker can output a calibrated
tone level to adjust the gain of the conference microphone(s) from
each conference room such that the tone level signal from each
microphone can be received at the calibration studio having a
substantially similar amplitude as the tone level signals from
microphones in the other networked conference rooms. The consistent
audio calibrations can enable people to remotely communicate while
feeling as if they are conversing within the same room.
One challenge with performing calibrations of audio equipment is
that relatively small changes in environment or room conditions can
cause measurable differences in the calibration. For example,
shutting curtains in a conference room, moving people, even
placement of books, folders, and computers on a desk within the
conference room can alter the acoustic characteristics of a room.
Determining whether a previously calibrated room is still within
calibration limits can be difficult due to changes of acoustical
properties of the room. In accordance with another aspect of the
invention, it has been recognized that that a networked calibration
conference room standard can be determined for each conference room
and stored in a database, such as the database 210 in the
calibration studio. The calibration standard can be used to
remotely determine whether a conference room is still within
predetermined calibration limits. Remote adjustment to one or more
speakers or microphones that are outside the calibration limits is
possible using the stored calibration standard as a reference.
More specifically, after the conference speaker(s) 236 and
microphone(s) 232 have been calibrated using the calibration studio
202, a calibration signature can be obtained for the conference
room. For example, a standardized audio signal can be transmitted
from the calibration studio 202 to the conference speaker(s) in the
conference room 206. Each conference speaker can successively
output the standardized audio signal and the output of each
conference speaker can be successively received by each conference
microphone, converted to a signature signal, and sent to the
calibration studio. The calibration studio can measure the
signature signal for each microphone and store a value for each
signal.
In one embodiment, the standardized audio signal can be an
acoustical impulse response configured to minimize changes in
calibration values due to acoustical changes within the room. One
type of acoustical impulse response that can minimize changes in
calibration values is an impulse response measured according to the
International Organization of Standardization (ISO) 3382 standard
for measurement of the reverberation time of rooms with reference
to other acoustical parameters. Other types of signals can also be
used for the standardized audio signal. Preferably, the
standardized audio signal can have a reduced amount of change due
to acoustical changes within the conference room caused by physical
changes within the room.
In one embodiment, each signature signal received from a conference
room can be stored in an M.times.N array comprising the signature
signal values of N speakers and M microphones. For a conference
room having three speakers and three microphones, a 3.times.3 array
can be formed, recording the signature signal value of each
microphone for each speaker. An example array, shown below, shows
the amplitude of the array of signature signals measured in
decibels.
TABLE-US-00001 Networked Conference Room Calibration Standard
Microphone 1 Microphone 2 Microphone 3 Speaker 1 4.2 4.4 4.6
Speaker 2 4.3 4.5 4.8 Speaker 3 4.1 4.3 4.7
A networked conference room calibration standard, comprising the
array of tone level signals, can be stored for each conference
room. The array can be stored on the network 204. In one
embodiment, the array can be stored in a database 210 in the
calibration studio 202. The database can then be accessed at a
later time and used to check a calibration of a selected conference
room.
The array provides a useful tool to determine if a conference
speaker or conference microphone calibration is outside
predetermined calibration limits, even when physical changes within
a conference room have altered the signature signal values. For
example, a selected networked conference room calibration standard
can be periodically verified by comparing a newly measured array of
signature signal values from each conference microphone for each of
the conference speakers in a selected conference room. It is
possible that changes within the conference room have caused
changes in the signature values between the two calibrations.
However, signature values for a selected conference microphone that
are compared across several speakers can show a trend. For example,
the signature values of speakers 1, 2, and 3 from microphone 2 in
the newly measured array may each be about 2.5 decibels (dB) lower
than was recorded in the database for the networked conference room
calibration standard. Thus, it can be determined that the gain on
microphone 2 likely needs to be increased by about 2.5 dB.
Similarly, the output of a selected speaker may have substantially
similar changes when the newly measured array of signature level
signals are compared with the networked conference room calibration
standard for the selected conference room. For example, the output
of speaker 3 may be about 3.5 dB greater as recorded by microphones
1, 2, and 3. The gain of speaker 3 can likely be reduced by 3.5 dB
to enable the speaker to be within the original calibration
limits.
Thus, the array can be used to remotely check a calibration of a
conference room and to make adjustments to speakers or microphones
when the signature values are substantially similar throughout at
least a portion of the array. The larger the number of speakers and
microphones that are in a conference room, the more accurately the
array can be used to remotely adjust the calibration of the
conference room to be within the initial calibration limits that
were recorded after a manual calibration. Of course, if
substantially different values are recorded throughout the array,
with no visible trend, it may be necessary to perform another
manual calibration.
Performing an initial calibration and maintaining the calibration
using the array and the calibration studio 202 can be accomplished
with the assistance of software. The software can include drivers
to operate the database 210, the measurement and source generation
device 212, the digital audio mixer 214 and the codec 216 in the
calibration studio. Software can also provide a graphical user
interface to interact with the calibration studio and to
communicate over the network to each conference room 206. Software
can similarly be used within the conference room to control the
codec 220, the audio signal processor, the conference microphone(s)
232, and the conference speaker(s) 236. Software can be used to
remotely control the conference microphone gain and the conference
speaker gain to enable the devices to be remotely calibrated.
The use of the array provides a significant improvement by enabling
the audio calibration of a plurality of networked conference rooms
to be periodically verified and corrected. The array enables
corrections to calibration levels of microphones and speakers that
change after an initial calibration while accounting for possible
changes due to physical and environmental changes within a
conference room. The ability to verify and correct conference room
audio calibrations allows each of the plurality of conference rooms
to retain substantially similar audio characteristics over time to
allow conference participants to meet and interact as if they were
within the same room.
While the forgoing examples are illustrative of the principles of
the present invention in one or more particular applications, it
will be apparent to those of ordinary skill in the art that
numerous modifications in form, usage and details of implementation
can be made without the exercise of inventive faculty, and without
departing from the principles and concepts of the invention.
Accordingly, it is not intended that the invention be limited,
except as by the claims set forth below.
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